Although an intense focus of medical research and development has been devoted to cancer immunotherapy and significant improvements have been made, cancer remains a major challenge in the healthcare industry worldwide. This major challenge is due, in part, to the ability of cancer cells to evade the monitoring mechanisms of the immune system, which is partly the result of inhibition and/or down-regulation of anti-tumor immunity. Still, development of in vivo systems to optimally determine the therapeutic potential of new cancer therapies that are designed to activate and/or promote anti-tumor immunity and determine the molecular aspects of how cancer cells provide inhibitory signals to immune cells (e.g., T cells) is lacking. Such systems provide a source for assays for assessing the therapeutic efficacy of candidate agents that promote an anti-tumor environment in vivo.